The BINGO project

VI. H I halo occupation distribution and mock building

¹ Center for Theoretical Physics of the Universe, Institute for Basic Science (IBS), Daejeon 34126, Korea
e-mail: jjzhang@shao.ac.cn
² Instituto de Física, Universidade de São Paulo, CP 66.318, CEP 05315-970 São Paulo, Brazil
³ Instituto Nacional de Pesquisas Espaciais, Av. dos Astronautas 1758, Jardim da Granja, São José dos Campos, SP, Brazil
⁴ Department of Physics and Astronomy, University College London, Gower Street, London WC1E 6BT, UK
⁵ Center for Gravitation and Cosmology, College of Physical Science and Technology, Yangzhou University, Yangzhou 225009, PR China
⁶ School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, PR China
⁷ IFSA Collaborative Innovation Center, Shanghai Jiao Tong University, Shanghai 200240, PR China
⁸ Unidade Acadêmica de Física, Universidade Federal de Campina Grande, R. Aprígio Veloso, Bodocongó, 58429-900 Campina Grande, PB, Brazil
⁹ Max-Planck-Institut für Astrophysik, Karl-Schwarzschild Str. 1, 85741 Garching, Germany
¹⁰ Technische Universität München, Physik-Department T70, James-Franck-Straße 1, 85748 Garching, Germany
¹¹ Instituto de Física, Universidade de Brasília, Brasília, DF, Brazil
¹² School of Aeronautics and Astronautics, Shanghai Jiao Tong University, Shanghai 200240, PR China
¹³ Departamento de Física, Universidade Federal da Paraíba, Caixa Postal 5008, 58051-970 João Pessoa, Paraíba, Brazil
¹⁴ Centro de Gestão e Estudos Estratégicos – CGEE, SCS Quadra 9, Lote C, Torre C s/n Salas 401-405, 70308-200 Brasília, DF, Brazil
¹⁵ Department of Physics and Electronics, Rhodes University, PO Box 94, Grahamstown 6140, South Africa
¹⁶ Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030, PR China
¹⁷ Kavli IPMU (WPI), UTIAS, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8583, Japan

Received: 25 March 2021
Accepted: 14 June 2021

Abstract

Context. BINGO (Baryon Acoustic Oscillations from Integrated Neutral Gas Observations) is a radio telescope designed to survey from 980 MHz to 1260 MHz, observe the neutral hydrogen (H I) 21 cm line, and detect the baryon acoustic oscillation signal with the intensity mapping technique. Here we present our method for generating mock maps of the 21 cm intensity mapping signal that cover the BINGO frequency range and related test results.

Aims. We would like to employ N-body simulations to generate mock 21 cm intensity maps for BINGO and study the information contained in 21 cm intensity mapping observations about structure formation, H I distribution and H I mass-halo mass relation.

Methods. We fit an H I mass-halo mass relation from the ELUCID semianalytical galaxy catalog and applied it to the Horizen Run 4 halo catalog to generate the 21 cm mock map, which is called HOD. We also applied the abundance-matching method and matched the Horizen Run 4 galaxy catalog with the H I mass function measured from ALFALFA, to generate the 21 cm mock map, which is called HAM.

Results. We studied the angular power spectrum of the mock maps and the corresponding pixel histogram. The comparison of two different mock map generation methods (HOD and HAM) is presented. We provide the fitting formula of Ω_Hi, H I bias, and the lognormal fitting parameter of the maps, which can be used to generate similar maps. We discuss the possibility of measuring Ω_Hi and H I bias by comparing the angular power spectrum of the mock maps and the theoretical calculation. We also discuss the redshift space distortion effect, the nonlinear effect, and the bin size effect in the mock map.

Conclusions. By comparing the angular power spectrum measured from two different types of mock maps and the theoretical calculation, we find that the theoretical calculation can only fit the mock result at large scales. At small scales, neither the linear calculation nor the halofit nonlinear calculation can provide an accurate fitting, which reflects our poor understanding of the nonlinear distribution of H I and its scale-dependent bias. We have found that the bias is highly sensitive to the method of populating H I in halos, which also means that we can place constraints on the H I distribution in halos by observing 21 cm intensity mapping. We also illustrate that only with thin frequency bins (such as 2 MHz), we can discriminate the Finger-of-God effect. All of our investigations using mocks provide useful guidance for our expectation of BINGO experiments and other 21 cm intensity mapping experiments.